In an ultrasonic diagnosing device, a voltage is applied to an ultrasonic oscillator made of a piezoelectric material to oscillate the same and thereby transmit an ultrasonic wave. Accordingly, the ultrasonic diagnosing device has a voltage generating circuit for generating a voltage that drives the ultrasonic oscillator. For example, reference can be made to the gazette of Japanese Laid-Open Patent Publication No. 2004-236869.
In the case that, for example, a battery is used as a power supply of the voltage generating circuit, a voltage supplied by the battery is a comparatively low voltage (specifically below 15V). Therefore, the voltage generating circuit is required to generate a high output voltage (specifically 20V-50V) from the comparatively low voltage. An inverse converter has been used in the past as the voltage generating circuit that meets said requirement, and said inverse converter is a switch hand-over converter using a transformer.
However, since the inverse converter uses the transformer, it is very hard to raise a switching frequency above a specified frequency. The required capacity of circuit components that includes the capacitance of capacitors on a mounting substrate is inversely proportional to a square root of the switching frequency in nature. So the higher the switching frequency is, the less the required capacity is, thus reducing volume of the circuit components. However, it is very hard to raise the switching frequency above the specified frequency in said inverse converter, so the volume of the circuit components cannot be reduced and miniaturization of the mounting substrate is almost impossible. Moreover, due to a height of the transformer of the inverse converter, it is very hard to realize thinning of the mounting substrate. It can be seen above that when using the inverse converter, the miniaturization and thinning of the mounting substrate are restricted.